U.S. Pat. No. 4,361,142 discloses a knee orthosis having a pair of knee joint assemblies 13 and 14 positioned on opposite sides of a patient's knee, each assembly having sidebars 15 and 16 extending alongside the upper leg and lower leg, respectively. The upper sidebars are in part held along the upper leg by a proximal femoral cuff consisting of a rigid or semi-rigid proximal interfacial member or plate 17 that is shaped to conform to the front (anterior) contour of the upper leg and is rigidly connected to the upper sidebars 15. A suspension strap 20 extends behind the leg and is adjustably connected to plate 17 (using Velcro patches or other ajustable connecting means) to form the proximal cuff about the wearer's thigh.
A second suspension strap 21 extends between upper sidebars 15 below the proximal cuff and, as shown in Figure 1 of the patent, extends only about the rear (posterior) portion of the upper leg. The purpose of strap 21 and pad 26 is to complement the suspending action of the proximal cuff and, in particular, hold the upper sidebars in proper positions against the sides of the wearer's leg. Two additional points or areas of suspension are located below (distal to) the knee, one being provided by a distal tibial cuff composed of interfacial element 18 and strap 20, and the other by a more proximal tibial cuff consisting essentially of interfacial member 19 and straps 23, 24.
As indicated in the patent, the purpose of the suspension cuffs is to immobilize the upper and lower sidebars 15 and 16 in relation to the leg in order to maintain the lateral and medial joints of the orthosis in position along opposite sides of the wearer's knee. While the orthotic joints described in the patent have been found effective in achieving the desired results if the sidebars 15 and 16 are sufficiently immobilized with respect to the upper and lower leg, some difficulties have been encountered in achieving such immobilization and avoiding "pistoning" or longitudinal shifting of the orthosis as the patient moves about. The problems occur more notable with physically active patients having strong muscular development of the legs but, in view of the fact that the orthosis is particularly suited for treating athletic injuries, a substantial proportion of the patients may be so characterized.